Installation of inflatable occupant restraint systems, generally known as “airbags,” as standard equipment in all new vehicles has intensified the search for smaller, lighter and less expensive restraint systems. Accordingly, since the inflator used in such systems tends to be the heaviest and most expensive component, there is a need for a lighter and less expensive inflator.
A typical inflator includes a cylindrical steel or aluminum housing having a diameter and length related to the vehicle application whereby the propellant is contained therein. The inflator is generally provided with an internal filter comprising one or more layers of steel screen of varying mesh and wire diameter. Gas produced upon combustion of the propellant passes through the filter before exiting the inflator. Particulate material, or slag, produced during combustion of the propellant in a conventional system is substantially removed as the gas passes through the filter.
Much research and development in gas generant technology has been devoted to reducing the smoke, soot and other particulates produced during combustion. Inhalation of the particulates by a vehicle occupant after airbag activation can be hazardous. Various gas generant formulations and inflator design have been developed in which the particulates resulting from combustion of the gas generant are substantially eliminated or significantly reduced.
Nevertheless, certain types of propellants are still desirable notwithstanding the relatively high percent of combustion solids produced, given favorable characteristics such as burn rate, sustained combustion, and repeatability of performance.
Other ongoing concerns with gas generators include the need to control the time period between activation of the igniter and initiation of gas generant combustion (especially in gas generators having multiple combustion chambers configured for supplying inflation gas to multiple inflatable elements of an associated system), and the need to increase manufacturing efficiency and reduce manufacturing costs.